Roles for c-Myc in Self-renewal of Hematopoietic Stem Cells*
- Yusuke Satoh‡,
- Itaru Matsumura‡§,
- Hirokazu Tanaka‡,
- Sachiko Ezoe‡,
- Hiroyuki Sugahara‡,
- Masao Mizuki‡,
- Hirohiko Shibayama‡,
- Eri Ishiko‡,
- Jun Ishiko‡,
- Koichi Nakajima¶ and
- Yuzuru Kanakura‡
- ‡Department of Hematology and Oncology, Osaka University Graduate School of Medicine, 2–2, Yamada-oka, Suita, Osaka 565-0871 and the ¶Department of Immunology, Osaka City University Graduate School of Medicine, Osaka 545-8585, Japan
- § To whom correspondence should be addressed. Tel.: 81-6-6879-3871; Fax: 81-6-6879-3879; E-mail: matumura{at}bldon.med.osaka-u.ac.jp.
Abstract
Notch and HOXB4 have been reported to expand hematopoietic stem cells (HSCs) in vitro. However, their critical effector molecules remain undetermined. We found that the expression of c-myc, cyclin D2, cyclin D3, cyclin E, and E2F1 was induced or enhanced during Notch1- or HOXB4-induced self-renewal of murine HSCs. Since c-Myc can act as a primary regulator of G1/S transition, we examined whether c-Myc alone can induce self-renewal of HSCs. In culture with stem cell factor, FLT3 ligand, and IL-6, a 4-hydroxytamoxifen-inducible form of c-Myc (Myc/ERT) enabled murine Lin–Sca-1+ HSCs to proliferate with the surface phenotype compatible with HSCs for more than 28 days. c-Myc activated by 4-hydroxytamoxifen augmented telomerase activities and increased the number of CFU-Mix about 2-fold in colony assays. Also, in reconstitution assays, HSCs expanded by c-Myc could reconstitute hematopoiesis for more than 6 months. As for the mechanism of c-myc induction by Notch1, we found that activated forms of Notch1 (NotchIC) and its downstream effector recombination signal-binding protein-J κ (RBP-VP16) can activate the c-myc promoter through the element between –195 bp and –161 bp by inducing the DNA-binding complex. Together, these results suggest that c-Myc can support self-renewal of HSCs as a downstream mediator of Notch and HOXB4.
Footnotes
-
↵1 The abbreviations used are: HSC, hematopoietic stem cell; 4-HT, 4-hydroxytamoxifen; SCF, stem cell factor; FL, Flt3 ligand; RBP, recombination signal-binding protein; CDK, cyclin-dependent kinase; Ab, antibody; RT, reverse transcription; EMSA, electrophoretic mobility shift assay; BM, bone marrow; h, human; m, murine.
-
↵* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
- Received January 14, 2004.
- Revision received March 18, 2004.
- The American Society for Biochemistry and Molecular Biology, Inc.
